1. Field of the Invention
The present invention is directed to methods of cleaning out wells using an inert gas. More specifically, the invention is directed to methods of cleaning out wells which employ an inert gas in a region of the well where collected matter has inhibited the ability of the well to produce. The inert gas, typically nitrogen gas, is supplied on-site by the separation of air using a membrane or a pressure swing adsorption system.
2. Background of the Related Art
In the cleaning out of oil or gas or geothermal wells, a fluid is typically delivered to a particular area of the well. For example, in a cleaning out operation, fluid must be introduced in the area of the well to be cleaned to remove the sand, scale or other substances that have effected the ability of the well to produce. One such fluid includes a foam consisting of nitrogen gas and liquid. Nitrogen can also be combined with a surfactant, foaming agent or water for different applications, like well treating.
One method of cleaning out a well includes the use of air cooled to cryogenic temperatures. The frozen air not only reduces the threat of downhole combustion but also freezes the ground to prevent the influx of water during clean out. As is well known, cooling to cryogenic temperatures is costly and requires additional heavy equipment which may not be readily available, particularly when the well is in a remote location like offshore. It is also common to use liquid nitrogen as the source of gas. Liquid nitrogen, however, is disadvantageous because it is considerably more expensive to use than air and difficult to obtain in remote locations.
It would therefore be desirable to devise a method by which an inert gas, typically nitrogen gas, may be conveniently and efficiently supplied to an area of a well to be cleaned out which eliminates the problems associated with cryogenic nitrogen and other sources of nitrogen gas.
The present invention is generally directed to a method for cleaning out oil and/or gas or a geothermal wells in which a compressed inert gas is delivered to the area of the well where production is inhibited. The inert gas is obtained from an on-site, non-cryogenic source. In particular, the source of the inert gas is air which is preferentially separated into an inert gas rich fraction and an oxygen waste gas fraction such as by membrane separation or by pressure swing adsorption, for example.